The present invention relates generally to an apparatus and method for reducing the circumference of a vessel, and more particularly to an apparatus and method for reducing the circumference of vascular structures, including cardiac valves.
All artificial or prosthetic heart valves, whether mechanical or bioprosthesis, although greatly improving the condition of the patient, have some serious drawbacks; namely thrombogenicity (tendency towards thrombus formation and subsequent detachment with embolization), and limited durability secondary to tissue structure failure.
Other complications such as noise, interference with hemodynamics, especially in smaller sizes, hemolysis (destruction of blood elements), risk of thromboembolism in all patients who receive mechanical valves, endocarditis (valve infection) and dehiscence of the valve also occur. Because of the risk of embolism, the majority of patients who receive artificial heart valves need to take anticoagulative medication for life with the concomitant risk of hemorrhage and necessary change in life style.
Different and more recent developments in the field of cardiac surgery included attempts to surgically repair diseased vascular tissue, in particular, heart valves. A variety of surgical maneuvers or procedures have been used for this purpose. This type of reconstructive surgery has been shown to be superior to valve replacement in many respects.
Reconstructive surgery, however, is generally more difficult to perform than replacement and is not always possible in every patient. Among the variety of reconstructive maneuvers, valve annuloplasty is the most frequently performed in the tricuspid and mitral valves. Valve annuloplasty is an operation which selectively reduces the size of the valve annulus. For this purpose, a number of prosthetic rings have been developed for the atrioventricular valves. One such well known commercially available ring is the Carpentier (distributed by American Edwards Laboratories) ring.
The Carpentier method of valvuloplasty employing the Carpentier ring is disclosed in the product pamphlet "Prosthetic Rings and Accessories for Tricuspid and Mitral Valvuloplasty", produced by American Edwards Laboratories in December, 1985.
Carpentier et al., U.S. Pat. No. 5,061,277 relates to a flexible cardiac valvular support prosthesis which is generally ring shaped and has a first length which is flexible and a second length which is less flexible than the first length, so the support may shape the annulus while the first length of the support in place in a heart valve annulus allows contraction thereof.
Carpentier et al., U.S. Pat. No. 4,917,698 relates to a multi-segmented annuloplasty ring prosthesis for use in the surgical correction of a deformed heart valve, which provides a substantially circular body comprising in part segments joined together by flexible joints, the body being shaped in proportion to the annulus of a heart valve.
Duran, U.S. Pat. No. 5,258,021 relates to a Sigmoid Valve Annuloplasty Ring in a scalloped shape having three sinusoidal struts to adapt to the anatomical shape of the annulus of the human sigmoid valves. The ring is made of a biocompatible material covered with a biocompatible cloth.
Lam et al., U.S. Pat. No. 5,104,407 relates to a selectively flexible annuloplasty ring for suturing to the annulus of a heart valve, the annular ring comprising a partially flexible length and a partially rigid length. The ring is covered in a suturable material.
Wright et al., U.S. Pat. No. 5,201,880 relates to Mitral and Tricuspid Annuloplasty Rings having a unitary construction with internal drawstrings and a semi-flexible stiffener in the anterior segment.
Cosgrove et al., U.S. Pat. No. 5,041,130 relates to an assembly for holding a substantially flexible lenticular shaped annuloplasty ring in a position for suturing about a valve annulus. The unitary annuloplasty ring contemplated therein is substantially flexible, and is partially circumferential, encompassing only the posterior mitral annulus.
Reed, U.S. Pat. No. 4,489,446 relates to an adjustable heart valve prosthesis with unitary construction including a dynamic stiffener element.
Gilbertson et al., U.S. Pat. No. 5,064,431 relates to an annuloplasty ring of tubular construction including drawstrings selectively adjustable to adjust the annulus to a desired shape.
Myers et al. U.S. Pat. No. 5,011,481 relates to a holder for an annuloplasty ring for use in implantation.
Commercially available annuloplasty rings have several drawbacks. First, they are expensive. Second, unless they are either rigid or sutured to the tissue annulus while still attached to a rigid holder, they may not provide a precise, predictable reproducible annuloplasty because of the unpredictable degree of longitudinal shortening along the circumference of the sutures within the confines of each mattress suture used to secure the ring to the tissue annulus. Each suture is necessarily tied with variable and unpredictable degrees of tension by the operating surgeon.
Third, most mitral rings are completely circumferential committing the operating surgeon to placing sutures in the anterior annulus where dilatation rarely occurs and where a tissue tear from inexact suture placement can produce significant mitral regurgitation. Fourth, a rigid mitral ring, because it is preshaped to an oval configuration, must be precisely placed or an unsatisfactory annuloplasty may result. Fifth, a rigid tricuspid ring can dehisce if not made to conform to the slightly spiral, nonplanar shape of the tissue annulus. Sixth, any rigid ring prevents the normal flexibility of the tissue annulus of the atrioventricular valve during ventricular contraction.
A need exists for an apparatus and method which provides a customized annuloplasty, tailored to the needs of specific pathophysiological situations, including but not limited to a limited annuloplasty or commissuroplasty of any valve annulus, a subtotal annuloplasty of any valve or a complete annuloplasty of any valve annulus. A need also exists for an apparatus and method which allows the repaired vascular structure to retain its flexibility in all planes while preventing further dilatation, or circumferential lengthening of the tissue annulus or vascular structure.
It has been found that to achieve such objects, a commercially available annuloplasty ring is not necessary. Such objects may be effected through use and implantation of an annuloplasty device comprising a series of discrete suture support segments.